1. Field of the Invention
The present invention relates to a display drive apparatus and a drive method thereof, and a display apparatus and the drive method thereof. In particular, the present invention relates to a display drive apparatus for drive a display pixel including a light-emitting element that emits light by receiving current, and a display apparatus including a display panel in which the display pixels are arranged in a plurality of rows that display image information and the drive method thereof.
2. Description of the Related Art
In recent years, a self light emitting-type display apparatus has been actively researched and developed as a next-generation display device following a liquid crystal display apparatus. A self light emitting-type display apparatus includes a display panel in which organic electroluminescence elements (organic EL elements), inorganic electroluminescence elements (inorganic EL elements), or elements such as light-emitting diode (LED) for example are arranged in a matrix-like manner.
When a self light emitting-type display using an active matrix drive method in particular is compared with a well-known liquid crystal display apparatus, this self light emitting-type display has a higher display response speed, a lower view angle dependence, as well as higher brightness, higher contrast, and image quality with higher definition and does not require, in contrast with a liquid crystal display apparatus, a backlight or a light guide plate. Thus, this self light emitting-type display using an active matrix drive method is very advantageous in having a further thinner thickness and a lighter weight. Thus, this self light emitting-type display is expected to be applied to various electronic devices in the future.
The self light emitting-type display using the active matrix drive method comprises, with regards to every display pixel, a light-emitting element and a pixel drive circuit structured to include a plurality of switching elements (transistors) for controlling the light-emitting status of the light-emitting element for example.
A gradation control method for this display pixel is mainly classified to a current-writing method and a voltage-writing method. In the current-writing method, gradation current having a current value in accordance with display data is supplied to a display pixel and a voltage component in accordance with a current value of gradation current is held in a pixel drive circuit to flow, based on the held voltage, drive current through a light-emitting element to control a light-emitting brightness. In the voltage-writing method, a gradation voltage having a value in accordance with display data is supplied to a display pixel to hold, in a pixel drive circuit, a voltage component corresponding to current flowing in accordance with the supplied gradation voltage to flow a drive current based on the held voltage component through a light-emitting element to control a light-emitting brightness.
The current-writing method can suppress, even when variation or dispersion of characteristics of a switching element of a pixel drive circuit is caused, an influence on drive current supplied to a light-emitting element and thus can realize a light-emitting operation with appropriate brightness and gradation in accordance with display data for a long period of time and in a stable manner. However, the current-writing method may cause a case where, when gradation current in accordance with display data having the lowest or relatively-low brightness is written to the respective display pixels, a writing time constant causes an increased time for charging a data line to cause a longer writing operation to prevent a previously-set writing time from providing a sufficient writing operation to cause a so-called insufficient writing to cause a deteriorated quality of a displayed image.
The voltage-writing method on the other hand can suppress the insufficient writing because current flowing when a gradation voltage is supplied to a display pixel can be increased. However, variation in characteristics of a switching element of a pixel drive circuit causes variation in a value of current flowing during a writing operation to cause variation in a voltage component held by a pixel drive circuit to cause variation in a value of a drive current flowing through a light-emitting element.